Wire tension control



June 15, 1954 c. THOMAS WIRE TENSION CONTROL Filed April 1'7, 1953INVENTOR Lewzls 6. 1120mm" $2M 9 laz /MW ATTORNEYS 3 3 Q m m a w 4 w wO. Y w w m m: mm Qw O P m mm: mm

Patented June 15, 1954 UNHTED STATS tTET OFFICE 7 Claims.

This invention relates to wire tension control devices, andparticularly, to an apparatus for maintaining uniform tension in a wireor the like being fed to a wrapping machine. It is desirable to wrapmany tubular objects, such as a concrete pipe, thin-walled tubing andthe like, with wire under tension to thereby prestress the tubularstructure and render it able to withstand great internal pressureswithout fracture. The apparatus of the present invention, however, maybe employed to tension wire being fed to and utilized by any othermechanism or apparatus.

In. general, the apparatus consists of a pulley or sheave engageablewith a run of the wire being fed to the wrapping machine and tensionapplying means arranged to constantly urge the pulley in a direction toapply tension to the wire and to maintain a uniform tension therein. Thepulley is mounted on a carriage or carrier to which a cable is attached,either directly or by means of a traveling pulley, and which cable isplaced under tension by having its other end held in fixed position andby having a weight suspended. from an intermediate portion of the cable.The magnitude of the weight determines the pull of the cable on thepulley and, therefore, the tension applied to the wire.

Since the rate of feed of wire may vary or its extent of elongation mayvary as the process proceeds, the weight may rise or fall and thecarriage or carrier may move through an impractically large range ofmovement. Too large a range of movement would necessitate an unusuallylarge and bulky apparatus. The present invention is concerned with meansfor regulating the range of movement of the tensioning weight andconsists of a winch to which the stationarily held end of the cable isattached and which winch is under control of the weight. If the weightsrise beyond a predetermined limit, the winch is actuated to unwind cabletherefrom and. thus lower the weights to the desired level without, inany way, changing or even momentarily disturbing the tension applied tothe wire. Likewise, if the weights drop below a predetermined lowerlimit, control means are actuated to wind more cable on the winch andthus raise the weights to the desired level.

It has been heretofore proposed to regulate the tension in a wire beingfed to a machine by I means of a weight. The prior art devices, however,engage the traveling wire directly by the weighted pulley and regulatethe rate of feed of the wire to keep the weight within the desired rangeof vertical movement. Such arrangements Cll are subject to manydisadvantages, since the control of the rate of feed must be exercisedwith extreme accuracy and at frequent intervals.

The present invention is not concerned with regulation of the rate offeed or" the wire being tensioned, but exercises control only on thelength of the secondary cable supporting the tensioning weight.

It is, therefore, an object of this invention to provide a simplearrangement of weights to impose uniform tension on a traveling wire.

It is a further object of this invention to provide a device fortensioning a traveling wire and which is free of adverse effectsoccasioned by vibrations caused by the traveling wire or the feed motortherefor.

It is a further object of this invention to provide a wire tensioningdevice wherein the tension may be regulated a desired amount without thenecessity of performing any complicated calculations.

It is a still further object of this invention to provide a wiretensioning device of unusually simple and economical construction.

Further objects and advantages will be readily apparent to those skilledin the art as the description proceeds in connection with theaccompanying drawings, wherein:

Fig. 1 is a schematic side elevational view of an apparatus embodyingthe present invention; and

Fig. 2 is an enlarged sectional view taken on the line 2-2 of Fig. 1.

The apparatus shown in the drawings schematically illustrates a machinefor wrapping wire under tension about a cylindrical concrete pipe 2, byway of example. It is to be understood that the wire being tensioned maybe utilized by any other suitable machine within the scope of thepresent invention. The concrete pipe 2 may be supported for rotationabout its longitudinal axis in any conventional manner and caused torotate about that axis to wrap a tensioned wire r about its outersurface. Further means (not shown) may be provided for moving the pipe 2longitudinally of its axis as wrapping proceeds, to maintain thatportion of the pipe being wrapped always in line with the path ofadvance of tensioned Wire 5. Such means are conventional and need not bedescribed further.

Wire 1 is supplied by a suitable reel 6 or other source of supply and isfed therefrom (such as by controlling rotation of the reel 6) at a ratecorresponding to the rate of rotation of the pipe 2. Preferably, thewire is fed from reel 6 at a somewhat lesser rate than it is wrapped onpipe 2 since placing the wire under tension increases its lengthsomewhat.

The apparatus for maintaining wire 4 under uniform tension comprises asuitable fixed framework 8 provided with a trackway H} on which acarriage I2 is mounted for movement. Although shown in the drawings as amere slide, the carriage [2 may be provided with rollers engagingtrackway It. The carriage I2 has a roller or pulley i4 journalledthereon at l6 and around which wire 4 is trained. It will be obviousthat wire 4 may progress from reel 6 to pipe 2 and merely causingrotation of pulley l4. Any force applied to carriage l2 urging it to theleft will maintain wire 4 under corresponding tension. The tension ineach run of wire 4 will be onehalf the force applied to carriage I 2.

The frame 8 also anchors one end i 8 of a cable 26. The cable 20 istrained about a second pulley 22 journalled on carriage I2 and extendsover an idler pulley 24 journalled in bearing block 25 and downwardlyinto a pit or other suitable space 28. Within the space 26 the cable 26is trained over a traveling pulley 28 then upwardly over a second idlerpulley 36 journalled on framework 32. Also mounted on the framework 32is a power driven winch 34 having a drum 36 about which the end of cable20 is wound. A suitable motor 38 may be arranged to drive the winch drum36 in either direction. The change of direction of rotation of winchdrum 36 may be effected by clutches and gearing, but preferably motor 38is a reversible electric motor.

The traveling pulley 28 in the pit or space 26 is journalled to a yoke40 having a rod 42 extending downwardly therefrom and terminating in ahead 44 underlying and supporting a platform 46. The platform 45 mayhave upwardly extending rods 48 fixed thereto (see also Fig. 2) adjacentthe corners of the platform. A plurality of weight elements 56 areprovided with openings near their ends corresponding to the spacingbetween rods 48 whereby the weight elements may be threaded on the rods48 to be held in position thereby on platform 46. Weight elements 50 maybe added or removed at will, to vary the tension of cable 2n andconsequently the tension applied to wire 4.

It will be noted that weights 56 are suspended from cable 26 by means ofa traveling pulley 28 and thus the tension in each run of cable 29 isone-half the total value of the weights 50 plus the platform and itsassociated structure. The cable 20, having its end 58 anchored to frame8 and passing over a traveling pulley on carriage [2, will apply a forceto the carriage i 2 equal to twice the tension in cable 25. In otherwords, the force applied to the carriage I2 is exactly equal to theweight suspended from cable 20 (ignoring friction). As statedpreviously, the tension applied to wire 4 is one-half the force appliedto carriage l2. It will, therefore, be obvious that the tension in wire4 may be readily and rapidly adjusted by adding or removing weights B inan amount equal to twice the desired change of tension in wire 4.

While the carriage i2 has been described as being supported by andguided along trackway I B, it will be apparent that in manyinstallations the track 16 can be eliminated. In such case the carriage12 will be suspended and held above the ground or other surface by thetension in wire 4 and cable 20.

Preferably the trackway It! is provided with at least one stop member 52positioned to be engaged by an end of carriage 12 to prevent unwantedmovement of carriage I2 beyond that stop position and consequent damageto control member 58, to be described. Likewise, bearing block 25prevents too great movement of carriage [2 to the left and thus preventsdamage to control member 56.

The weights 50 are so positioned on platform 46 that an edge 54 of theplatform extends laterally outwardly beyond the weights. A pair ofcontrol members 56 and 58 are mounted on the side walls of the pit orspace 26 and each is provided with a plunger or the like 6!} arranged inthe path of movement of the edge 54 of platform 46. The upper controlmember 58 is positioned to be engaged by the platform 46 at about thetime carriage l2 approaches stop 52 and the lower control member 56 ispositioned to be engaged by platform at about the time carriage 12reaches the leftmost limit of its travel on trackway Hi. In the positionshown in Fig. 1, platform 46 is slightly below control member 58 andplunger 60 of control member 53 is just free of contact with platform46. Assuming that under these conditions wire 4 is being continually fedto and wrapped on pipe 2, platform 46 and weights will maintain uniformtension in the wire without vertical movement. If for any reason therate of feed of wire 4 slows down or an enlarged portion of wire isbeing tensioned so that its elongation is lessened, the platform 46 willrise slightly as a result of movement of carriage E2 to the right.Assuming that platform 46 rises sufiiciently to actuate plunger 60 ofcontrol member 56, a circuit consisting of suitable wiring in duct 52 isclosed by a switch controlled by plunger 66 and energizes motor 36 torotate winch drum 36 in a direction to unwind some of cable 26 from thedrum. Such unwinding of cable 20 will increase the length of the cablebetween idler pulleys 24 and 36 and thus lower the platform 46 to againrelease plunger 66 and de-energize motor 38. At that time the weight ishanging free and performing its intended function.

The winch drum 36 is thus a mere holding means or reaction member forcable 26 but is capable of being manipulated to change the length of theloop of cable 29 extending downwardly between idler pulleys 24 and 36.Other mechanisms could be employed for accomplishing the same function.For instance, the leftmost end of cable 20 could be anchored to a membermovable along framework 32 and that member could be caused to move tothe right or left in response to actuation of control members or 58.

The control member 56 is arranged in the motor circuit to energize themotor for rotation in a reverse direction from that described above, ifand when the weights 56 and the platform 46 descend far enough to engagethe plunger E6 of control member 5'5 and the result will be lifting ofplatform 46 to clear the control member 56 and again stop motor 38.

From the above description it will be apparent that applicant hasdevised an apparatus for maintaining uniform tension in a traveling wireand which will maintain that tension uniform without the necessity ofconstant adjustment even upon rather large variations in the rate offeed of the wire or variations in its degree of elongation.

The arrangement described for limiting the range of vertical movement ofthe weight not only reduces the overall size of the apparatus, but alsoinsures accurate control of the tension in wire t. If the weight werepermitted to descend in space 26 an unlimited distance, a substantialweight of cable (between pulleys 2d and 30) would add to the effectiveweight of the tensioning arrangement. By limiting the range of movementof platform is, the variation in the weight of cable 253 between pulleys24 and 3B can be held to an inconsequential value.

While a single specific embodiment of the invention has been shown anddescribed, it is to be understood that many modifications may beresorted to without departing from the invention as defined in theappended claims.

I claim:

1. Wire tension control apparatus comprising, a trackway, a carriagemovable along said trackway, a pulley journalled on said carriage andadapted to engage an intermediate portion of a wire to be tensioned, acable connected to said carriage and arranged to pull said carriagealong said trackway in a wire tensioning direction, the other end ofsaid cable being wound on a winch drum, reversible drive means arrangedto drive said winch drum in either direction, spaced idler pulleysbetween said carriage and winch drum, said cable being trained over saididler pulleys and looped downwardly therebetween, a vertically movableWeight supported by said loop, vertically spaced control means arrangedin the path of movement of said Weight, the uppermost control meanscausing said drive means to rotate said winch drum in a cable-unwindingdirection when said weight engages said control means, and the lowercontrol means, when engaged by said weight, causing said winch drum torotate in a cable-winding direction.

2. Wire tension control apparatus as defined in claim 1 wherein saidcable is trained over a second pulley journalled on said carriage, theend of said cable being anchored to a stationary structure.

3. Wire tension control apparatus as defined in claim 1 wherein saidweight comprises, a platform, a pulley riding on said downwardly loopedcable, said pulley being journalled to and supporting said platform, anda plurality of individually removable weight elements on said platform.

4. Wire tension control apparatus as defined in claim 3 wherein saidweight elements are positioned inwardly of an edge of said platform andwherein said vertically spaced control means are positioned in the pathof movement of said edge.

5. Wire tension control apparatus as defined in claim 1 wherein saiddrive means comprises a reversible electric motor and wherein saidcontrol means comprise motor control switches adapted to, respectively,energize said motor for rotation in dilierent directions.

6. Wire tension control apparatus comprising, means having a pulleyjournalled thereon adapted to engage an intermediate portion of a wireto be tensioned, a cable connected to said means and arranged to pullsaid means in a wire tensioning direction, said cable being alsoconnected to a holding apparatus comprising a cable take-up and let-outdevice spaced from said means, the portion of said cable between saidcarriage and holding means being trained over guide means to form adownwardly extending loop of said cable, a weight suspended from saidloop and being freely movable along said cable whereby to tension saidcable and urge said means in a wire tensioning direction, and meansresponsive to vertical movement of said weight beyond upper or lowerpredetermined limits to actuate said take-up and let-out device to,respectively, increase or decrease the length of cable in said loopwhereby to maintain said weight at all times within the range defined bysaid limits.

7. Wire tension control apparatus as defined in claim 6 wherein saidweight includes removable weight elements whereby the tension applied tosaid wire may be readily adjusted.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,412,509 Johnstone Dec. 10, 1946 2,635,825 Stanford Apr. 21,1953

